How to Subnet a Network Part I

very Smith here again and we've come to the point to where we will actually start talking about how to subnet and start walking you through the whole subnetting procedure first and foremost there's a couple things that I really want to make sure that you understand first it is it's highly unlikely that you're going to be a subnetting master after viewing this video so if you're not completely sure or if this doesn't you know if you if you think to yourself I don't completely get it that's actually perfectly fine and very much Noble at this point you know you've probably never submitted before in your life therefore it takes a little bit before we actually get into what's here on this board and I explained everything to you a couple of things that a couple more things I want to point out one hopefully you've watched the other videos that shows the IP addressing it shows the classes how to convert binary numbers all those things actually lead up to this another thing inside of the doc sharing in the classroom right now should be a Excel spreadsheet that has all of this information here on it on the spreadsheet that you can get and print out and kind of use it to follow along so if you want to pause this video and go back to the class and pull up that excel spreadsheet and doc sharing it should simply be called subnetting information inside of the doc sharing in class that would be good too lastly this video is going to be a little bit longer I try to keep all the videos to about 10 minutes or less but this video is going to be a little bit longer because this just for par is a little bit more time to explain this but it should be time well spent because subnetting is an extremely important part of any type of Network administration and for those of you in the Cisco class the certification tests the first Cisco certification test is probably about 60% subnetting so the more you know this the better it's going to be for you in the real world as well as certification tests so enough of that let's get to it and let me try to explain to you what I have on the board if you've seen earlier videos or if you saw the earlier video where I showed you how to convert binary to decimal and decimal to binary then you recognize here at the bottom we have what we call our binary calculator it is this little chart here at the bottom that will help you convert binary numbers to decimal numbers and vice versa wonderful holy tool to have I use this all the time even when I take certification tests till I go in and write this thing down if I know who's going to be IP addressing and subnetting on the test now here behind me on the left hand side of the board what I have essentially done if you look at it is I took the binary calculator and I just kind of stood it up because the same numbers that you see down here are actually here 1 2 4 8 16 32 64 128 exactly like it is over here the difference is is that if you look to the very far left we have a 2 to the power of number so we have 2 to the power of 0 to 2 1 to 2 2 squared 2 cubed 2 to the 4th 5th 6th and 7th now this is going to play a very important part in our subnetting when we get here to step 5 if we get to it just a little bit we say 2 to the N the 2 to the N in the end is one of these two to the power of numbers and it'll make more sense to you in just a little bit so again so far all these videos hopefully have made things a little bit easier and you see that this is not very difficult and I'm here to tell you I know the disease for me to say this but this is not very difficult either so let me show you how to subnet broken subnetting down into what I call the six rules of subnetting or six steps of subnetting and you see these over here steps 1 through 4 if you've seen the other videos that I've shown you step one through four is easy you can do it in your head in fact it shouldn't take you very long to do in your head anyway what I do beg of you though is don't skip a step even when you get really good at this go through all the steps in your mind you don't have to write them down maybe but just go through it in your mind step one step two step three because it just gets you in a really good rhythm I cannot tell you how many students I've seen in the past where they would they get really confident which is great but they would get really confident it would skip a step and then before you know it you know they get wrong answers because they kind of confuse themselves don't do this you know stick with it now when you're dealing with subnetting there are two basic types of subnetting the two basic types of subnetting are what I call the easy way which is this here and the hard way which is this here now the hard way I need to say the hard way forgive me for though the quotes like them but the hard way is not very hard in essence what it means is this if you have two sub sub meant doing the quote-unquote hard way that means you need to go through all six steps over here to submit the easy way whenever you see a subnetting problem that looks like this that has a slash and a number at the end you really kind of be thinking yes you know that's a that's a win because with the easy way the only thing you have to do is you just literally skip to step six because step one through five has been done for you and again I'll explain more about that here just a little bit so the hard way all six steps the easy way this way up here you only have to go to step number six which is obviously easier once to have the null six so let's look at these steps quickly and then I'll kind of walk you through a couple of examples of subnetting and hopefully it will be your head we'll spend too much and hopefully you'll actually think hey that would quite as hard as I thought because it's really not that difficult so if you look at our rules here we start with rule number one it says ID the class ID the class is meaning IV it's either an a B or C that's it step one is done step two is you want to identify the network and node IDs remember in a previous video I told you that depending upon what class you have certain our tests represent the network ID and then other octants represent the node or host ID and that's it step two is done once you identify those you're done step three is apply the default subnet mask well the default subnet mask for a B or C is wherever you see the network ID of the IP address if it's a Class A remember the network ID is the first octet well a default subnet mask is you want to put a two five five wherever the network ID is so Class A the subnet mask would be 255.0.0.0 for Class B remember Class B the first two octets was your network ID so the subnet mask would be 255.255.0.0 and for Class C the first three octets were your network ID so that would be 255.255.255.0 so you're essentially applying the default subnet mask for whatever class it is that you identified in class and step number one next step number four is you want to convert the subnet mask to binary and this is where your binary calculator will come into play a little bit I say a little bit because converting a default subnet mask is very easy if you see a 255 in the subnet mask then that 255 equates to eight ones in your octet so if you see 255 it's eight ones eight one eight bits eight ones if you see a zero in the subnet mask then it's a zeros it's that simple so with a standard subnet mask our default subnet mask I should say it's either going to be eight ones or eight zeros and that's it so steps one through four is really again you know pretty basic IP stuff things you should have already read in your book and hopefully things you already know step 5 and step 6 are the only two that's where you actually have to get into I guess you would say math and even these two steps are not very difficult believe it or not I know again it's easy to me to say so step five says use two to the enth - to you I should say use the formula two to the nth - - to determine the custom subnet mask now what does this mean now if you remember in one of the other videos I showed you I use the example of a pizza as like a network you have one whole pizza or one whole network and what you're trying to do is subnetting is we want to take that one whole network and we want to break it into smaller pieces and those pieces are going to be easier for us to manage and control well we just have to figure out how do we break that up and the custom subnet mask in this formula that we're going to use is going to tell us the numbers that we have to put in to mathematically break it up into smaller pieces that's all really is to it so what we have to do is we have to change the subnet mask from something other than default to a custom subnet mask that will mathematically give us those pieces or those smaller subnets that we're looking for we'll walk through a couple of examples and kind of show you so that's step five step six is once you determine the custom subnet or once you have the custom subnet mask you want to determine something called the LSB and LSB stands for least significant bit and the least significant bit will be the bit in the octet that you're changing and again you'll see in here in just a minute it's the bit and the octet that you're changing the smallest bit in that on tenth that still has value in other words the smallest bit that has a one in it and that's what's called your least significant bit and believe it or not the least significant bit is the key to your subnetting as far as like determining your range and where your subnets are going to begin and end once you get that least significant bit it's it's everything else just will fall into place believe it or not so these are your six steps and again I don't expect you you right now you may be thinking yourself I don't understand the word you just said and that's fine it is you're just learning so don't don't freak out yet it's it's very common once you walk through a couple of these once you see a couple of these it usually is a lot easier for you to comprehend than others understand and that's my hope so let me go back over here to the easy way and the hard way like we talked about and let me explain to you why this is called the easy way or wow that's what I call it that's not what anybody else calls it the slash and a number here at the end is often referred to as cider notation CIDR cider cider notation and what makes this so easy is that they have already done steps one through five for you this in essence believe it or not that number right there is your custom subnet mask and what this number represents in this after the slash this number represents how many ones binary ones you're going to have in your subnet mask now there's a rule a tcp/ip rule about subnet masks that you must adhere to and that rule is a very simple rule but it states that your subnet mask will start with binary ones and those binary ones must be continuous until they stop so in other words you're going to start with binary ones there will be all binary ones until you stop and from that point on there must be the rest zeros and if you will recall from the other videos and from also your reading in your studying you have 32 total bits that you're going to be dealing with so what this number here tells us is that the first 20 of those bits are going to be binary ones which means that the last 12 in this case will be zeros so this is giving us our custom subnet mask the only thing we would have to then figure out at this point is what's the least significant bit and once we figure out the least significant bit we have pretty much everything we need for to give us our ranges and to tell us how many subnets we're the subnets begin where they end and all that other kind of good stuff now on the quote-unquote hard way to do it which is this way here this one you start off with nothing in essence all we have is a what I call a starting point and where did I get the starting point where did this IP come from well I made it up you're the network administrator at your company you will be able to make up a starting point and I'm going to use this as almost like a base or a base line to then build my sub networks off of so the 170 to 1600 that you see here that's just me making it up and it's that simple and that's what network administrator's do they think you're the starting point they go from there now if you look right above that it says that we need eleven networks needed and what that means is that means that I need to create eleven sub networks so this particular method Dakota quote hard way I would need to go through all six steps to determine what the numbers and and where I'm going to be in and again if this is starting to be confusing to you please don't freak out I totally understand it's not quite as bad as you think so let's go through this let's let's walk through this one right here the hard way because if you can do the hard way you can do the easy way really easy so it says here that we this is our starting point and we need eleven networks so if we use our submitting rules and we go through it let's see if we can make this thing work so 170 2016 done zero none zero what class is that what class IP address is this hopefully you are saying B because this is a Class B IP address remember the first octet is the words of the octet you determine your class and this octet is between 128 and 191 so this is a Class B so step one is done not very hard is it so step one is Class B in this case step to identify the network and node IDs well if you remember on a Class B IP address the first two octets represent the network and the last two architects represent the note so what I'm gonna do is I'm just going to draw a line right here in between them and just separate them just like that it's that simple step two is done step three says apply the default subnet mask well I told you just a little bit ago for a Class B IP address your default subnet mask will be 255.255.0.0 wherever you see wherever the network ID is the the subnet mask of the number below it will always be 255 you know for a standard Class A B or C and you can we'll explain more about that later on in other videos so apply the default subnet mask is step three step four says to convert the subnet mask to binary so in other words we have to take this number and we have to convert it to binary well again a default subnet mask is a very simple conversion because wherever you see 255 that's been an equate to eight ones in our binary calculator because all of these numbers added up together would give you 255 so this would be one two three four five six seven eight dot one two three four five six seven eight dot and then zeros would be eight zeros one two three four five six seven eight dot one two three

Channel: Berry Smith

Views: 76,265

Rating: 4.9630485 out of 5

Keywords:

Id: gOOPP-ceToc

Length: 16min 31sec (991 seconds)

Published: Tue May 16 2017